The purpose of this investigation is to evaluate the application of a direct current to stimulate bone ingrowth into porous aluminum oxide. Porous cylindrical samples have been implanted into medullary canal of canine femora, both in the cancellous and cortical bone regions. Constant current (10 micro a) power packs are implanted on one side and maintain the implat site at a relative negative potential with respect to the surrounding soft tissue. The contralateral side is used as a non electrically stimulated control. Tissue ingrowth is evaluated using a mechanical push-out test, microradiography and histological thin sectioning. A protocol has been established whereby each method of evaluation can be performed on each implant. The interfacial shear strength and tissue microstructure are studied as a function of implant residence site and time.